Changes of plasma free amino acid concentrations and myofibrillar proteolysis index by starvation in non-pregnant dry cows.

摘要

The effects of 5 day starvation on urinary metabolite excretion, plasma metabolites and free amino acid concentrations in four non-pregnant dry cows were investigated. Starvation significantly reduced (P<0.05) the bodyweight and faeces weight. The plasma glucose concentration decreased (P<0.05) during days 2-5 of starvation. Starvation significantly increased (P<0.05) the plasma nonesterified fatty acid concentration. The plasma urea nitrogen concentration and urinary urea nitrogen excretion increased transiently (P<0.05) at days 1 and 2 of starvation. The plasma 3-methylhistidine concentration was significantly higher (P<0.05) at days 2, 3 and 5 of starvation. However, the urinary 3-methylhistidine excretion was significantly higher (P<0.05) at days 4 and 5 of starvation, not corresponding to the change in the plasma. Starvation did not change the plasma proline, methionine, lysine and total amino acid concentrations. On the other hand, starvation reduced (P<0.05) the plasma aspartic acid, serine, asparagine, glutamic acid, glutamine, alanine, tyrosine, tryptophan and histidine concentrations. Plasma glycine increased during starvation. Plasma threonine, isoleucine, leucine and branched-chain amino acid increased (P<0.05) by prolonged starvation. The results of this study indicate that prolonged starvation accelerated myofibril protein degradation in non-pregnant dry cows and apparently consumes most glucogenic amino acids in preference to other amino acids.